Deflection control system



sept- 23, 1952 F. J. DARKE, JR 2,611,816

DEFLECTION CONTROL SYSTEM attorney sept. 211952 F. J. DARKE, JR 2,611,816

DEFLECTION CONTROL SYSTEM Filed Feb. 28. 1948 l 3 Sheets-Sheet 2 VERT/WL 'CONTROL HZSYNG riventor Franas .l Darke, Jr.

Cttomeg F. J. DARKE, JR

DEFLECTION CONTROL SYSTEM Sept. 23, 1952 2,611,810

Filed Feb. 28, 1948 3 Sheets-Sheet 3 Zhwentor Francis Darke Jn Gttorneg Patented Sept. 23, 1952 DFLECTION CONTROL SYSTEM FrancisJ. Darke, Jr., Princeton, N. J., assigner to Radio Corporation of America, a corporation of Delaware 'Y ApplicationFebruary, 1948, Serial No. 12,083

This invention relates to scanningraster accuracy control and more particularly to methods and circuit arrangements for improving registration of selected component or primary colorV images in a simultaneous color television system.

The transmission of images of iinite detail and discontinuous or limited moti-on by electricity has best been solved by the process of scanning which consists of moving anexploring element, spotor point over the image to be transmitted in Ya periodically repeated path cover-ing the total image area. The exploring `element generates `a signal which indicates the brightness of the image area at the instantaneous position of'lthe explor ing point. The signal-is then transmittedlover the communication channel to the `reproducing station where alike spot or point whose brightness is controlled 4by the signal and whose `movement is insynchronism with the exploring ypoint at the transmitting station causes an image to be l reproduced.

In order to obtain geometrical-ly accurateand natural proportions -in image reproduction,Y it iis necessary that lthe' transmitting `and receiving rasters be similar.- .1 f f According to the U. S. patent to GeorgefL.

Beers, No. 2,385,563, dated September 25, 19455;y

the velocity of an exploring point is converted into a frequency which .is compared toa stand, ard frequency of a tuned circuit. .Any change in frequency '.or phase is employed to 'providea con trol potential which may -varylin'both magnitude and polarity. This contr-ol potential may be used' in -any desired manner, rior example, it .may be used to vmaintain synchronism or to control .the velocity-of anrexploring. point, such as the end'oiY a moving stylus or thespot produced by anveiectron :bea-m irnpingingon `a surface which is to bei explored. The last named examplewill .be recognized as being of particular `value inthe .television art.

.lt `has YVbecome .quite lfamiliar .to the television art that images in substantially their Ynatural color may be reproduced at a remotelocation by not only dividing theim'agesinto'elemental areas and transmitting electrical signals representative of the intensity .of the :various elemental areas, but by also dividing .an image 'into selectedLco'mponent colors whichvmay Vbe transmitted ,in fsevouence over an electrical circuit :for .utilizationat a receiving station. Y A f l -A more satisfactorymethod lfor transmitting images in substantially their natural colorhas become known as the simuli',a neousf -rnethodgv wherein signals representative of each of thesei claims; (c1. 17a- 5.2)

are transmitted simultaneouslyv over separate electrical circuits. Thecomponent color images are then superimposed in optical registry at the receiving station to'form a color image.

It Willbe appreciated,however, that the superpositioning of component color images mustv be accomplished to a reasonably high degreeof ac curacy in order to provide for satisfactory color images at the receiving stations.

it will be appreciated that such a requirement can be met only by employing 'scanning rasters having a high degree of accuracy. v

The co-pcnding U. S. application of Ray D. Kell, ySerial No. 772,978, filed September 9, 1947, and* entitled Scanning System, shows and describes arrangements andmethods for improving scanning accuracy and providing precise registrationv of a plurality .of Vscanning rasters in a vertical direction. According to .the U. S.

application of R.. D.' Kell referredto Iimmediatelyabove, .the scanning target has av :control .element or areahaving .a selected edge extending along a scanning line. Circuit arrangements are connected ftothe elements inrsuch a manner as to derive an electrical .indication of Vtherelative posi.- tion of the point :of scansion With regard to the selected .edge of the .control element. cuit arrangements then provide 'a ."raster posi.- tioning signal to furnish `accurate vregistration with other scanning rasters: .x f According 1to- `this invention, .methods .andarrangements are fprovidedior improving scanning accuracy and .establishing .improved registration between a pluralityoff scanning' rasters.v

Accordiiigto this invention. an optically regis-- tere-d pattern-fisA associated with each scanning raster; lhepattei-n is scanned tvo-'form an'alternatingvoltage Whose amplitudeis indicative ofY relative position in `a'l'rst or vertical direction' and whose frequency is indicative of therelative` velocity of the exploring point. The alternating voltage is .converted into a yirst control voltage by detection to control the position of they exploringpoint in the first or vertical direction,

while a second-control voltage is `developedby A primary object or" this inventioniszto.impiotve `scanningLacci'lracy. L 1 Anctl1er..object ofthis invention to :permit The .cir-

accurateI registration of a plurality of independent scanning rasters.

Another object of this invention is to improve the registration of color television images.

Other and incidental objects of the invention will be apparent to those skilled in the art from a reading of the following specification and an inspection of the accompanying drawing in which:

Figure 1 shows by block diagram one form of this invention;

Figures 2 and 3 indicate schematically the operation of this invention;

.Figure 4 illustrates an electron beam target in accordance with one form of this invention;

Figure 5 shows in block a portion of another form of this invention;

Figure 6 shows by circuit diagram a ratio detector suitable for employment in the practice of this invention;

Figure 7 shows by circuit diagram still anotherf form of this invention;

Figure 8 shows by circuit diagram another form of this invention;

Figure 9 illustrates by circuit diagram a suitable keying arrangement with associated delay network suitable for employment in a memory circuit which may be employed in connection with this invention;

Figure l0 shows in block the employment of this invention with a memory circuit of the type shown and described in detail in the co-ncurrently filed U. S. application of Alda V. Bedford, entitled Scanning Control System, Serial No. 12,091, filed February 28, 1948 (D-26l65) and Figure ll shows graphically the operation of the arrangement shown in Figure 10.

Turning now in more detail to Figure 1, there is illustrated a television camera tube I which, for the purpose of example, has been illustrated as an image orthicon including an image section and an electron multiplier. The details regarding the image orthicon and its mode of operation are quite Well known in the television art and are believed to be sufficiently well shown and described in published literature to obviate the necessity of a detailed description here. A complete description of the image orthicon television pickup tube may be found in an article entitled The Image Orthicon, A Sensitive Television Pickup Tube, publishing in the Proceedings of the Institute of Radio Engineers for July 1946.

The inclusion of the image orthicon in a television camera may be found well described in an article entitled Image Orthicon Camera published in the "RCA Review for March 1946.

It is not intended that the operation of this invention be limited to the image orthicon type of camera tube, but the practice of this invention will-also be found advantageous for use with other types of camera tubes, such as the popular iconoscope.

The image pickup tube l obtains light from object 3 through a partially silvered mirror 5 and a lens system 1.

The video signal obtained from the camera tube I is employed in any of the Well known manners, such as the modulation of a television transmitter.

- In the practice of this invention, it is necessary to generate in the image pickup tube I an auxiliary signal which is employed for scanning defiection correction.

According to one form of this invention,.as illustrated in Figure 1, this auxiliary signal is 4 obtained by the employment of an auxiliary screen 9, which is suitably illuminated and caused to project an image on the sensitive electrode of tube I. The image of the screen 9 projected on the target electrode of tube I produces a charge pattern of the type indicated on the screen 9. The charge pattern causes to be generated during the scanning operation a grillf frequency. The explanation regarding :the generation of this grill frequency may best be understood by ya brief referen-ce to Figure 2, which shows a greatly enlarged section of the pattern formed at the target electrode af image pickup tube i.

Let it be assumed, for example, that the light from screen 9 of Figure 1 forms a charge pattern wherein areas of increased charge are indicated by the squares of Figure 2. Areas of reduced charge are indicated by the screen-like sections surrounding the squares. If, now, it is assumed that the scanning element; or exploring point is positioned. as illustrated and designated I I, its horizontal movement across the charge pattern will generate an alternating voltage whose amplitude is governed kby its vertical position, while the frequency of the alternating voltage is governed by its velocity. This will be more readily understood when the position of the scanning element I3 is examined. When the element is travelling horizontally at a height I3, it will be seen that a greater portion of the increased sensitivity areas is intercepted, thus generating in the auxiliary or grill frequency voltage a greater amplitude. Likewise, when the exploring point is at position I5, its horizontal movement does not intercept much of the increased sensitivity area so that the amplitude of the generated auxiliary alternating voltage is not great.

Referring back now to Figure 1, the filter grill frequency I'I is employed to separate the auxiliary alternating` voltage of grill frequency from the video signal. The output signal of the filter I1 is then applied to a detector I9.

In accordance with the well known theory of operation of detectors, the output of detector I9 is a direct current potential whose amplitude is proportional to the alternating voltage passed by lter Il.

This direct current voltage obtained from detector I9 is then applied to the vertical deflection arrangement of image pickup tube I to provide a correctionin the deection. For example, if the position of the exploring point is at I3 of Figure 2, it may be assumed that the output of detector I9 inV producing a large direct current voltage causes in the vertical deflection arrangement 2l a force which will tend to pull the exploring point downward. On the other hand, if the exploring point is at position I5 of Figure 2, the output voltage of detector i9 is low, and therefore the effect of the direct current voltage from detector I9 is lesser and the exploring point tends to raise.

Vertical deflection arrangement 2I, the source of deflection synchronizing voltage 23 and the horizontal deflection arrangement 25 are shown in block inV view of the fact that no particular phase discriminators, any deviation of the grill frequency obtained from filterV l 'l with respect to the standard grill frequency obtained from block 29 :will result in a change in direct .current voltage which is applied to horizontal deiection arrangement 25. Suitable phase discriminators fin the form of a ratio detector and frequency discriminators will be described in detail below. Y

It Awill be seen, therefore, that if the velocityr of the exploring point exceeds a predetermined amount, a direct currentpotential obtained from phase discriminator 27 will tend to slow down the speed of the exploring point -in horizontal deection arrangement 25, while iff the exploring point is travelling at too'slowa speed, a control voltage will be applied lto horizontal Adeflection arrangement which Vwill tend to speed up the exploring point inits traverse.

"Although the practice of this inventionis applicable to linear type scanningwherein each succeeding scanning line is traversed immediately following the preceding scanning line, another form of this invention is applicable to the popular interlaced type of scanning wherein one eld of scanning involvingonly the odd lines is lfollowed by 4a secondA field of scanning involving only the even lines. t

Although the form ofthe invention shown in Figure 1 is also suitable for interlaced scanning, another form of the invention is 'illustrated in Figure y5, which is particularlyapplicable tothe interlaced type of scanning.

Turning now to Figure 3, which illustrates the operation of this invention as lapplied to int'er laced scanning, it will be seen that the control of Vthe vertical position of the scanning or exploring point 3| will be opposite in direction'toV that of 'the control of the exploring pointl-i. Let it be assumed that odd lines are along'the .upper edges of the areas and 31, while even lines are along the lower edges of the areas 35'and 31. This'is indicated by the exploring point/3l in the even line, while exploring point 33 is in the position of the odd line.

'It becomes apparent that during odd lines, the vertical control must be inverted with rre-s spect to the vertical control during even lines.

In accordance with the practice of this invention, this is accomplished by the employment of circuit arrangements illustrated in block as Figure 5.

Voltage from the detector, such as detector i9 of Figure 1, is applied to two keyed amplifiers 39 andlll. A square wave eld frequency indicated by block 4? alternately switches keyed ampliers 39 and 4| into operation during alternate field scannings the polarity of the energy obtained from keyed amplifier 39 in orderthat the vertical deflection correction voltage may be applied to the vertical deflection arrangement, as indicated by block 2| of'Figure 1. i A i Keyed amplifiers and polarity reversers are believed to be suiiciently well known to the radio art that they need n o detailed description here.

Turning now in detail to Figure '4, there is illustrated another form of this invention in-` volving a special electron beam target which eliminates the necessity of having the. screen A polarity reverser 45 reverses 9 the partially `silvered mirror. 5 of the form of theinvention shown in Figure i. f l

The electronfbeam .target of Figure .4 .takes a formawherein there a'reauxiliary .areas .'offfrayf generation material whose radiations may be picked up lby suitable electrical.means. It will be seen that during the scanningiof'th'e pattern, the .electrical current orelectrioal .voltage'formed by th'ef scanning operationas .a resultof `the'ger'ie` eration of rays 'will bel suitable. for .employment for control of defiectionLin `accordance iwithvfthis invention. It `has also Ybeen .proposed-to provide a'target having* areas of invisible light. sensi?` tivity` By isuitably'forming the .areas inaccordance with-the .teachings vof thisL inventionzzand utilizingauxiliary sources of invisible lightfelec.- tric .control-'voltages may. "he generated 'which will be fsuitable for usejin connection withf/the control arrangements taught by this invention? .Turningnow to Figure 6, there is Villustrated a ratio'detector suitable for employment in fthe practice' of this invention.- The ratio detector illustrated Ais wellv shown .and'described inan article entitled New Ratio Detector Simpliiies FM Receiver Design.l by Stuart W. Seeley, pub?- lished in Broadcast News." for January, v194:61 Tube d'lobtains the grillfrequency from the camera tube and applies it through suitable coul-r pling arrangements to vdouble diode 51, which produces in its output circuit a signal train whose amplitude is equal to the ratio of the grill fre*- quency obtained from the 1camera tothe naturalfrequency of the tuned circuit 55. e v The function and operationof the' discriminatorfas applied to this invention may best b'e understood by a review of its theory of opera tion.rv Such review maybestbe made by reference not only to the ratio detector illustrated by circuit-diagram in Figure 6, but bytincluding in the discussion of the theory off operation the' popularfrequency discriminator employed inthe circuit' diagramof the form of ltheinvention shown in Figure 7. lhefollow-ing discussion will therefore bedirected to boththe ratiodete'ctor of Figure and the discriminator of Figure `I7,'1wherein likefe'lementdesignations refer toelik'e elements. 1 Inductanc'es-l-Li rand L2 form Aan-"interstage coupling transformer tuned to the' desired stand--Y ard or grill frequency. v'.lhevoltage at Ea in fthe primary induces a vvoltage inl-the secondary which, for thepurposes -of discussion,` may bei divided into two components, En and Ec. The induced voltage in the secondary is fed to theianodes of a pair of diodes-as shown. However. there is also a direct connection from one side of Li-to the center of L2. This'placesLg directly inthe cathode return circuit of the diodes. Thus the total voltage on the anode of the first diode (VT-l) is Ea-i-Et'. .These voltages must, of course, be added vectorially. When the frequency ofV the voltage from the input circuit is 'equal to the resonant frequency of the tuned circuit,fthe voltage in the secondary is out'of phase with that in the primary. The voltages El andEz, which are fed'to the diodes, are equalfand the D.-.C. outputof the. diodes is alsoequal. 'Since the output connections ofthe diodes are oplOSed inthe discriminator of Figure v'1, no voltage will appear' at the output terminals. .Y y Y f Let us now consider whaty happens when` the input voltage frequency is different from Athe resonant` frequency of the tuned circuit, as-:will occur if theyelocity 'of the exploring point, de;-V viates from a desired.v standard. The. secondary voltage leads the primary voltage by something less than 90. The voltages E1 and E2 fed to the diodes are now diiferent, and the rectified outputs are also of different values. Thus, a D.C. voltage proportional to the frequency deviation ofthe input signal is caused to appear at the output terminals.

An important characteristic and a decided dis'- advantage of this standard discriminator circuit of Figure 7 is that it is also sensitive to amplitude fluctuations of voltage in the input circuit. It is therefore necessary in employing the discriminator of Figure 7 that there be provided ahead of the discriminator a limiter tube 63, as illustrated, the operation of which is also well known to the art. The output voltage of the limiter tube 63 is substantially constant, regardless of input voltage. The reason for the' effect of amplitude on the discriminator circuit-may be understood when it is appreciated that the voltages En, Eb and Ec vary proportionately with amplitude modulation, but E1 increases more than E2, thus causing distortion in the output circuit as a result of variations in amplitude of the input circuit. This is, of course, eliminated by the employment of a limiter tube 63.

.However, the ratio detector illustrated in Figure 6 is insensitive to amplitude modulation, and hence requires no limiter stages. The reason for this may be understood by comparison of the circuit diagrams of the ratio detector and the discriminator. As Will be noted, the input sections of both circuits are similar. The voltages fed to the diodes in the ratio detector are the same as those in the standard discriminator, and they vary with frequency swing in exactly the same manner. However, in the ratio detector the di odes are connected in series so that the D.C. voltages Which they develop are additive rather than being opposed, as in the discriminator circuit. Moreover, the sum of these voltages (Er-PE2) is prevented from varying at alternating voltages by the bypass condenser Ca While the sum of the diode output voltages E1 and'Eg is thus held constant, the ratio of these voltages varies as the ratio of the input voltages. Thus, if control connections are madeat points P and B, a control voltage proportional to the frequency swing of the input voltage is made available. Inthis way the ratio detector provides for'phase or frequency discrimination equally as good as the standard discriminator and free from the latter's unwanted sensitivity to amplitude modulation.

`It will be seen, therefore, that suitable control voltages may be obtained for employment in the practice of this invention. f

There is provided an auxiliary horizontal coil 6,1 in the output circuit of the discriminator. Auxiliary horizontal coil 67 may be coupled to the discriminator through an amplifier, if necessary. It will be seen that the voltage provided the auX- iliary horizontal coil is dependent upon the frequency of the signal applied through limiter tube 63 with respect to the tuned circuit 65. A portion of the grill frequency is applied to the detector or rectifier 69 across the tuned circuit 1i, which passes only the grill frequency. Detector 69 recties the grill frequency and applies it to an ampliiier tube 13 which furnisheskeyed amplifier tubes I5 and 71 with a directvoltage which is proportional to the amplitude of the alternating voltage in tuned circuit 1I. Y

Bysuitable employment of a multivibrator, as indicated, driven in synchronism with the field synchronizing signal. the output of detector tube 69 is inverted in alternate fieldsto be applied to the vertical control coil 19 for vertical correction in accordance with the vprocedure employed with interlaced scanning, as described in connection with Figure 3 above.

' The' keyed amplifier tubes l5 and 11 furnish control energy to vertical control coil 19, which is associated with the deiiection arrangement to provide suitable vertical correction information. Coil 19 may, as illustrated, be shunted` with a biasing arrangementincluding batteryl and variable resistor 83. It will be seen that by employing battery 8| and resistance 83, a suitable adjustment may be provided to eliminate any current iiow in coil 'I9 except when correction voltage is necessary.

Turning now to Figure 8, there is illustrated still another form of this invention wherein the grill frequency obtained-as a result of the scanning operation is applied to diodes 9| and 93, which are arranged in a bridge circuit involving resistances and 97.

A standard or grll'frequenc'y is applied to tube 99 and converted into a push-.pull voltage in tube IUI. rIhe push-pull voltage is alsoapplied to the bridge circuit involving diodes 9i and 93. It is therefore possible to obtaina. phase comparison between the standard frequency applied to tube B9 and the grill frequency-.applied to the bridge circuit. The output voltage of the bridge circuit involvingdiodes 9| and 93 is controlled by the relative frequencyof the input alternating voltages. This control voltage obtained from diodes Si and 93 is applied to tube 183, which contains in its output circuit a resistor IE5 which is included in the" normal horizontal sawtooth deflection generator circuit involving the horizontal coils |01. The theory of operation of the circuit shown in Figure 6 is well 'shown and .described in the copending U. S. applicationof G. L. Fre-V dendall lentitled Automatic Frequency Control System, Serial No. 547,355, led July 3l, 1944. There are, of course, other suitable phase and frequency discriminators for employment in this invention, such as that phase detector shown and described in the copending U. S. application of Allen A. Barco entitled Phase Detector, Serial No. 776,986, iiled September 30, 1947, wherein a simpliiied phase detector for automatic frequency or phase control systems and the like is provided by obtaining a D.C. control voltage from a control electrode of a. triode upon whose anode has been impressed'energy from one frequency generatorY and upon whose cathode is impressed a synchronizing voltage.

It must be remembered that all scanning processes are usually a series of discontinuous movements of the exploring point and are somewhat analogous to the movement of our line of sight when reading a printed page. Although the scanning control processes referred to above are Well adapted for maintaining. accuracy during any continuous scanning movement of an exploringpoint, or in systems having reasonably accurate scanning, normally, the correction information necessary for starting any continuous scanning movement of the exploring point is lost between continuous movements. For example, during the scanning of a single field, which is generally recognized as the scanning over the extent of the image area, the information relative to the correction at the beginning of the scanning of the field is immediately lost, so that the exploring element may not start the scanning of the succeeding iield from exactly the same position.

` 1,31 and 133.6

egeiijeie l'It isi also 'true that if; the inaccuracy offscanningl-shuuld-ailow the exploring-element tozde- Viaite from thedesir'ed position by'a-relatively great v'a1`noi 1nt, the necessaryv correcting information-would not -be available vand proper registrati'on could notf be had. fif f 'According tothe. invention shown'and-described inthe. concurrently iiled U.' S..l application of-'Alda V. Bedford', Serial Nol 12,091,1iled-February 28, 1948, `-(D-25165f)', therev is provided a method and circuit 'arrangement for remember'- ing'the necessary' correcting voltagebetween continuous scanning movements-'of theexplori-ng point. 'Afcondenser is charged'withthe developed correction voltageL at the beginning of any continuous scanning movement, and at the beginning 'of the next succeeding continuous scanning move'- ment or at'the'beginning of each succeeding field scanningffthe charge inthe condenser is 'ernployed'for position control tor-accurately position the-'exploring elementi" f f Another form of this 'invention shown-in Figure I() illustrates theutilizationllof this invention'in connection With-the memory' circuit arrangementstaught by the aforementioned' Bedford application. 2:' il v `In accordance With'tli'e theory, outlined at'the beginning of this speciiication that television images 'ifi substantially their"v natural color 'may be reproduced at a' remote location by dividing the images into selected component colors, an arrangement 'is illustratedY in Figurev 10* whereby-- a particularly b enencialapplication of this inventionffi's employed to "register component color images-" imagepickup tubes 'il l, -Hf'e -n v1HE are 'provided'ivith-associated cornponent'color filters l H,

HS- andlzl which, for the purpose or example,

are designated as red, blueandgreen lters.

It will be seen that' the 'video signals' ofimage pickupjtubestl I3Y and.` `|5 may be utilized'ior radio' transmission andv will; if' r rjo; ie';rlyjreceived, provide 'are image insubstannauy its' naturali color; l j

It is, ci course, importan t thatthe beaccurately registered'.v j though not shown, 'a suitable optical light dividing' arrangementV is `provided' jto kcause the component color images to'beproje'cted ontargets. |273, |25; and |21.l There isf also provided, in accordance with the teachings: ci the televisionv art such as the copending U.' vS.` application` oi John 4Evans referred to "alcol/e.; an arrangement to provide an auxiliary rayfupQon the vs cain'ii'r'ig 'images ray is picked up, for examplesinphotocell 'gaenefthe 'targepleieetreees' l 2.3 ne i: is provided with af pattern Whichis positioned-1n Optical registryas related toethe impressed-image.: V

Control.energy from 4photocell |3|v ispassed. to detector |35 and phase discrirni-natorl |f 3"|Y through band pass yfilter |-39a in accordancewith theexplanation of the operation of. thisf inventionabove. a

vControl, voltage from detector |35 is passed to' vertical deflection coil MI, while correctionvoltage from phase discriminator is passed-:to horivertical-memory line-to-line, switch M5, controlled by delayed and shaped line synchronizing Cil pulse, which connects condenser |41 into the control circuit for a short interval of time during the beginning of each scanning line. It will be seen that the charge on condenser |41 `will control the correction at the beginning of each scanning line in accordance with the correction obtained at the beginning off the preceding scanning line.

It isnecessary, however, that thecondenseri'l be discharged during the eld return time i-n o rder'notto carry over'the correction from the beginning of vthe last line of aveld to the beginning of the rst line of the next succeeding Afield. VThis i'sfaccomplished by key-ing' switch ||9 with` a ii'eld synchronizing pulse. .f5-Vertical` memory eld-t'o-'eld is also provided by a condenser and switch combihationjasindicated in the dotted block designated vertical memory viieldto'ffield.v

simuar circuit arrangements are employed for horizontalA memoryl line-todine andhriz'onis illustrated Figure 9i..

v(`; J'ndenser i"55, which is employed as a memory condenser in the control 'circuitjis switched into the circuit by the diode. arrangementv shoivn' in FigureV 9. The operation of such circuit isiwell knovvn to the art and functions toprovidea closed circuit. `only during the impressed synchronizingv pulse'tirneintervah The associated delay circuit, illustrated in' Figure 9 appropriately delays'the synchronizing pulse Vin order'that it will occur duringactual line or vfield scan'ningti'rnel t The delayof the synchronizing pulse. isbest il.- lustrated in Figure 11, wherein curve al illustrates the synchronizing pulse,'either1ine or eld, While curve b 'illustrates the associated sav/tooth Wave employed for deflection. Curve c shows the posil tion with respect. to time ot the. delayed, syn.-

chrofnizing pulse which is employed tocontrol the. switches in the circuit.

Althoughthe explanation of this invention is limited to certain applications. and. forms, it is not. intended that the practice of the invention, shouldbe limited thereto. The circuit arrange- I mentsrprovided in .the various forms of thisinventioninay b eernployed with any deflectioncircuit, Whether they be forasingle scanning tube` ore-Whether they be employed in a multiple system. l The explanation of the operation of thisinvention has also been directed particularly to image pickup; devices. It is, of course, important'to remember, that the practice of this/invention may not? necessarily vbe limited thereto, but may be applied' with equal advantages to image reproducing systems. 1 Y

Having thus described the invention,'what is claimedis;l f'

1. A control `system comprising inA combination, 'means for optically developing a checkerboard type pattern bearing a'relation to a desired scanning raster, meansv forV scanning said pattern with an exploring point to form an alf-y ternating voltage whose amplitude is indicative of relative position in a first direction and whose frequency is indicative of the relative velocity of said exploring point, means for developing a first control voltage from said alternating voltage by rectication, means for developing a second control voltage from said unrectifled alternating voltage by frequency comparison with a predetermined frequency, and means for controlling the position of said exploring point in said first direction with said first control voltage and controlling the velocity of said exploring point with said second control voltage.

2. A scanning control system comprising, means for forming a crossed line charge pattern bearing a form relation to a desired scanning raster, means for scanning said charge pattern with an exploring point to form an alternating voltage whose amplitude designates relative vertical position of the exploring point and whose frequency designates relative velocity of the exploring point, means for developing a vertical control voltage from said alternating voltage by generating a direct voltage proportional to the amplitude of said alternating voltage, means for developing a velocity control voltage from said alternating voltage by frequency comparsion with a standard alternating voltage, means for controlling the vertical position of said exploring point with said vertical control voltage, and means for controlling the velocity of said exploring point with said velocity control voltage.

3. A system for generating scanning control voltages comprising in combination a distinguishable pattern, an exploring point, a deflection arrangement to cause said exploring point to scan said pattern in a predetermined scanning raster, said pattern distributed in repeating spaced areas along linesoriented inthe direction of line scanning, a lter circuit responsive only to the signal frequency generated by the scanning of said pattern, a detector connected to said filter circuit to convert said alternating voltage` into a direct voltage, a frequency discriminator connected to said filter circuit tov compare the frequency of said alternating voltage with a standard frequency, a Vcontrol connection between said detector and Said beam deflection arrangement to control the scanning in a vertical direction, and a control connection between said frequency discriminator and said beam deflection arrangement to control the scanning in a horizontal direction.

4. A system for obtaining voltages for scanning control purposes comprising in combination a target to receive an exploring point, a deflection circuit arranged to cause said exploring point to scan said 4target in a predetermined scanning raster, means associated with said target for generating as a result of said scanning a scanning control voltage varying in amplitude at a predetermined frequency, the extent of its variation in amplitude depending upon the position of the exploring point with respect to a desired line of scanning, and the frequency of said control voltage depending upon the velocity of said exploring point with respect to a desired velocity, a detector connected to said aforementioned means, a frequency discriminator, a control connection between said detector and said beam deection arrangement to control the scanning in a vertical direction, and a control connection between Said frequency discriminator and said beam deflection arrangement to control the scanning in a horizontal direction.

5. A system for obtaining voltages for scanning control purposes comprising in combination a target to receive an exploring point, a deflection circuit arrangedy to cause said exploring point to scan said target in a predetermined scanning raster, means associated with said target having a periodically interrupted edge positioned along each desired scanning lineposition for generating as a result of said scanning a scanning control voltage varying in amplitude at a predetermined frequency, the extent of its variation in amplitude depending upon the position of the exploring point with respect to a desired line of scanning, and the frequency of said control voltage .depending upon the velocity of said exploring point with respect to a desired velocity, a rectier connected to said aforementioned means, a frequency discriminator, a control connection between said rectifier and said beam deflection arrangement to control the scanning in a vertical direction, and a control connection between said frequency discriminator and said beam deflection arrangement to control the scanning in a horizontal direction.

6. A system for obtaining voltages for scanning control purposes comprising in combination a target to receive an exploring point, a deflection circuit arranged to cause said exploring point to scan said target in a predetermined scanning raster, means optically associated with said target having a periodically interrupted edge positioned along each desired scanning line position for generating as a result of said scanning a scanning control voltage varying in amplitude at a predetermined frequency, the extent of its variation in amplitude depending upon the position of the exploring point with respect to a desired line of scanning, and the frequency of said control voltage depending upon the velocity of said exploring point with respect to a desired velocity, a detector connected to said aforementioned means, a frequency discriminator, a control connection between said detector and said beam deflection arrangement to control the scanning in a vertical direction, and a control connection between said frequency discriminator and said beam deflection arrangement to control the scanning in a horizontal direction.

'l'. A system for obtaining voltages for scanning control purposes comprising in combination a target to receive an exploring point, a deection circuit arranged to cause said exploring point to scan said target in a predetermined scanning raster, a pattern optically projected on said target having a periodically interrupted edge positioned along each desired scanning line position for generating as a result of said scanning a scanning control voltage varying in amplitude at a predetermined frequency, the extent of its variation in amplitude depending upon the position of the exploring point with respect to a desired line of scanning, and the frequency of said control voltage depending upon the velocity of said exploring point with respect to a desired velocity, a detector connected to said aforementioned means, a frequency discriminator, a control connection between said detector and said beam deflection ar rangement to control the scanning in a vertical direction, and a control connection between said frequency discriminator and said beam deflection arrangement to control the scanning in a horizontal direction.

8. A system for obtaining voltages for scanning control purposes comprising in combination a target to receive an exploring point, a deflection circuit arranged to cause said exploring'point to scan said target vin a predetermined scanning raster, an electrical current forming pattern associated with said target, said pattern shaped in repeating and spaced areas and having edges along the position of a desired scanning line, a detector connectedV to receive the electrical current formed by said pattern, a frequency discriminator connected to receive the electrical currentl formed by said pattern, a control connection between said detector and said beam deflection arrangement to control the scanning in a vertical direction, and aY control connection between said frequency discriminator and said beam deflection arrangement to control the scanning in a horizontal direction.

9. A system for obtaining voltages forscanning control purposes comprising in combination a target to receive an exploring point, a rdeflection circuit arranged to cause said exploring point to scan said target in a predetermined scanning raster, an electricalcurrent forming pattern associated with said target,n said pattern shaped in regularly7 repeating and spaced areas and hav- `ing edges along the position of each desiredscanning line, a detector connected toV receive the electrical current formed by said pattern, Ta frequency discriminator connected to receive the electrical current formed bysaid pattern, a control Ycoi-intrection between said detector 'and saidrbeamdeflection arrangement to control 'the scanning vin a vertical direction, and a control connection between said frequency discriminator and said beam deection arrangement to control the scanning in a horizontal direction. 1 I f 10. A system for obtaining voltagesfor scanning control purposes comprising in combination a target to receive-an exploring-point, a deflection circuit arranged to cause said exploring p'oint to scan said target ina predetern'iinedscanning raster, an electrical current forming pattern associated with said target, saidv pattern shaped in repeating and spaced areas and having edges along the position of a desired scanning line, a detector connectedY to receive the. electrical current formed by said pattern, a frequency discriminator connected to receive'the electric'alcurrent formed by said pattern, said frequency discrimi" nator arranged to receive a standard'ffrequency control signal, a control connection between said detector and .said beam deflection arrangement to control the scanning Vina vertical direction, and a' control connection between said frequency discriminator' and said beam deflection arrangement to control the scanning in a horizontal'direction.

11. A system for obtaining voltages for scanning control purposes comprising in combination a target to receive an exploring point, a deection circuit arranged to cause said exploring point to scan said target ina predetermined scanning raster, an electrical current forming pattern associated with said target, said pattern shaped in repeating and spaced areas and having edges along the position of a desired scanning line, said areas of different sensitivity compared to the remaining area of said target, a detector connected to receive the electrical current formed by said pattern, a frequency discriminator connected to receive the electrical current formed by said pattern, a control connection between said detector and said beam deection arrangement to control the scanning in a vertical direction, and a control connection between said frequency discriminator and said beam deflection arrangement to control Vthe scanning in a horizontal direction.

12. A system for obtaining voltages for scanning control purposes comprising in combination a target to receive an exploring point, a deflection circuit arrangedto cause said exploringpoint to scan. said. targetv in a predetermined scanning raster, an electrical current vforming pattern associated with said target, said pattern shaped: in repeating and spaced areas and. having' edges along the position of a desired scanning line, said areas of increased light sensitivity compared to the remaining area of saidr target, a detector connected to receive the electrical` current formed by said: pattern, a frequency'discriminator connected' to receive the electrical currentv formed by said pattern, a control connnection between said detector and said beam deflection 'arrangement to control the scanning in a Vertical direc'- tion, 'and a control connection between said frequency discriminator and said beam deflection arrangement to control the scanning lin a horizontal direction. f

13'. A system for obtaining voltages for scanningcontrol purposes comprising in combination a target to receive an exploring `point, a deflection circuit arranged to'cause said` exploringl point to scansaid target in a'predeterminedjscanning raster, an lelectrical currentforming pattern associated vwith said target, said pattern shapediri repeating and spaced areas, said spaced areas having edges along the position of a desired scanning line,'said areas' being of conducting mate# Yria-La Ydetector connected to receive the electrical 'current formedby said pattern, a frequency dis-l criminator connected to receive Vthe electrical current formed by said pattern, a control connes-- tion between said detector and saidbeam. delicotion arrangement to controly the scanning in; a vertical direction, and a control connectionbetween said frequency discriminator and lsaid beam ldeflection arrangement tocontrol the v'scany ning in a horizontal direction.

14.` A system for obtaining voltages for scan ning control purposes comprising inA combina-f tion a target to receive an exploring point, adeiiection circuit arranged to cause said exploring point to scan said target in a predetermined. scanning raster, an electrical current forming pattern optically projected onA said targetsaid pattern sha-pedin repeating and 'spacedareas having edges along the position ofthe desired scanning lines, a detector connected to receive the electri- 'cal current formed. by said pattern, afrequency :discriminatori connected to receive the electrical current formed by said pattern, a control connection between said detector and said beam deiiection arrangement to control the scanning in a vertical direction, and a control connection between said frequency discriminator and said beam deflection arrangement to control the scanning in a horizontal direction.

15. A system for obtaining voltages for scanning control purposes comprising in combination a target to receive an exploring point, a deflection circuit arranged to cause said exploring point to scan said target in a predetermined kscanning raster, an electrical current forming pattern optically projected on said target, said pattern shaped in repeating and spaced areas having edges along the position of the desired scanning lines, a detector connected to receive the electrical current formed by said pattern, a frequency discriminator connected to receive the electrical current formed by said pattern and electrical current of a predetermined frequency, a control connection between said detector and said beam dciiection arrangement to control the scanning in a vertical direction, and a control connection between said frequency discriminator and said beam deiiection arrangement to control the scanning in a horizontal direction.

16. In a color television system involving a plurality of selected component color images, a system for obtaining voltages for scanning control purposes to improve registration of said images comprising in combination a target for each selected component color image, each of said targets adapted to receive an exploring point, separate deflection circuits arranged to cause each of said exploring points to scan said targets in a predetermined scanning raster, an electrical current forming pattern associated with each of said targets and mutually registered, said pattern shaped in repeating and spaced areas having edges along the position of the desired scanning lines, a separate detector connected to receive the electrical current formed by each of said patterns, a separate frequency discriminator connected to receive the electrical current formed by each of said patterns, a control connection between each of said detectors and its associated beam deflection arrangements to control the scanning in a vertical direction, and a control connection between each of said frequency discriminators and its associated beam deflection arrangement to control the scanning in a horizontal direction.

17. In a color television system involving a plurality of selected component color images, a system for obtaining voltages for scanning control purposes to improve registration of said images comprising in combination a target for each selected component color image, each of said targets adapted to receive an exploring point, separate deflection circuits arranged to cause each of said exploring points to scan said targets in a predetermined scanning raster, an electrical current forming pattern associated with each of said targets and mutually registered, said pattern shaped in repeating and spaced areas having edges along the position of the desired scanning lines, a separate detector connected to receive the electrical current formed by each of said patterns, a separate frequency discriminator for all but one of said component colors and connected to receive the electrical current formed by its color associated pattern, a comparison connection between each of said frequency discriminators and the pattern for which there is no frequency discriminator, a control connection between eachof said detectors and its associated beam deflection arrangements to control the scanning in a vertical direction, and a control connection between each of said frequency discriminators and its associated beam deflection arrangement to control the scanning in a horizontal direction.

18. A system for generating control voltages comprising in combination a target to receive an exploring point adapted to form a scanning raster thereon, lmeans associated with said target to form an electrical charge pattern at said target, said charge pattern arranged in strips oriented in a rst direction and in a second direction perpendicular to said iirst direction, the strips oriented in said rst direction having edges positioned along scanning lines of said scanning raster and the strips which are oriented in said second direction arranged Vto produce an alternating voltage of a predetermined frequency during scanning, means for deriving an alternating voltage upon the scanning of said charge pattern, means connected to said means for deriving an alternating Voltage to convert said alternating voltage into a direct voltage, the amplitude of said direct voltage proportional to the amplitude of said alternating voltage, means connected to said means for deriving anl alternating voltage to compare the frequency of said alternating voltage with a predetermined frequency, a control connection between said means to convert said alternating voltage into a direct voltage and said beam deiiection arrangement to control the scanning in one direction, and a control connection between said means to compa-re the frequency of said alternating voltage with a standard frequency and said beam deiiection arrangement to control the scanning in another direction.

FRANCIS J. DARKE. Jn.

REFERENCES CITED The following references are of record in the file of this patent:

v n UNITED STATES PATENTS Number Zworykin Jan. 28, 1947 

